doc: doc lifetime of n-api last error info
Document the lifetime of the structure returned by napi_get_last_error_info
Fixes: https://github.com/nodejs/abi-stable-node/issues/251
Checklist
-
make -j4 test
(UNIX), orvcbuild test
(Windows) passes -
documentation is changed or added -
commit message follows commit guidelines
Affected core subsystem(s)
doc, n-api